Azure-sdk-for-js: Create a samples folder from the root with the README

[kaerm]

We need a readme that describes all the places where samples can be found placed in the /samples root directory that in the future will store samples that work across services:

For context, this is the .NET samples readme that Krzysztof wrote (it's okay to copy paste and adjust links and samples per language):
https://github.com/Azure/azure-sdk-for-net/blob/master/samples/README.MD

cc: @ramya-rao-a

[ramya-rao-a]

I like the general format used in the .Net readme but listing samples for each libraries will not scale. Would suggest having a bulleted list of libraries that link to individual sample folders

The common set of "how to guides" are helpful and can link to docs we have in the Documentation folder

cc @bterlson, @xirzec

[xirzec]

Seems reasonable to link to a README inside specific sample folders that list out each individual sample

[willmtemple]

@kaerm Is there anything in this that isn't addressed by the work for #5679 ?

[kaerm]

Nope, this issue is fully addressed by https://github.com/Azure/azure-sdk-for-js/pull/6998